The Ghost in the Atom: A Discussion of the Mysteries of Quantum Physics (Canto) [Paperback]

This book is a must read for everybody... It explain in a very simple way the idea "behind" Quantum theory. It explains the problems that quantum theory has raised, i.e., do things exist when we are not looking at them, or do they only exists because we are looking at them... The interviews part is very good; we get to know what physicists think of quantum theory, and what they think will happen to our way of looking to the world...

Anyone who is interested to understand reality (universe, consciousness and life), and laws of physics applicable to them must be interested in learning about the laws quantum mechanics. A number of books are available, and this one stands out as a book for good introduction. The authors' interview eight physicists who are actively engaged in research and the profoundness of the universe and the concept of quantum reality begins to unravel as you progress through the book. The book is written for common readers but you must appreciate basic quantum physics experiments, whose results are discussed throughout the book. There are nine chapters, and the first chapter introduces the basics of quantum theory.

Matter at the most fundamental level has both particle and wave nature (wave-particle duality), because some experiments illustrates the particle properties, and other experiments shows the wave properties. In addition, the Heisenberg Uncertainty principle postulates that the position and momentum of a fundamental particle are not determinable at the same time. This is not due to experimental limitations but inherent characteristic of matter, an intrinsic fuzziness of the subatomic world. Therefore it follows, in experiments measuring the path of fundamental particles; the famous two - slit electron experiment of Thomas Young; identical experiments yield different results. It is a common experience in the real world that the laws of cause and effect dictates common sense, for example, a planet in its orbit uses a well defined path and its position can be predicted at any give time, but in quantum world, this is uncertain and we can only discern the point of departure and point of arrival of an electron in an experiment but nothing about the actual path.

There are five major interpretations of quantum theory, they are; a. Copenhagen interpretation; b. Hugh Everett's many universes interpretation; c. Wigner's interpretation; d. Hidden variables interpretation and quantum potential; and e. Ensemble (statistical) interpretation. Copenhagen interpretation is considered as the official view. According to this, reality of classical world is ambiguous and non-specifiable. It gives subatomic particles an abstract mathematical status but does not provide reality in full common sense of the word. In classical thought the universe is independent of an observer; it exist no matter we observe that or not. This is objective reality that squares off with common sense perception. This is precisely the concept that Bohr challenged in his interpretation that objective reality doesn't exist per se until measurements are performed. In general, a quantum state may contain an infinite number of superimposed quantum states. The act of observation and measurement will result in one quantum state and others disappear instantaneously. Many universes interpretation of Hugh Everett proposes that superposition of wave function result in splitting the universe into multiple units each corresponding to one particular wave function or one state. The observer also splits into the same number of units and each universe will have a copy of the observer.

According to Wigner's interpretation, the quantum phenomenon does not happen until reality sets into the consciousness of the observer, but John Wheeler states that realty may have occurred but not put to use until this information is communicated.
Ensemble (statistical) interpretation which implies that any quantum mechanical measurement made is made on an ensemble of identically prepared systems. Hence the results of experiment take the form of a probability distribution of particular values for the measurement. This interpretation looks at the statistics and do not care about individual event. Hidden variables interpretation postulates that a particle like an electron has a potential called quantum potential (QP) which is a new property. Its effect does not depend on its magnitude but only on its form (particle or wave nature) so that it may have big effects over long distances. This wave (QP) also carries experimental arrangement with it and also the states of all other particles in the system. This interpretation also suggests that a particle has both position and a definitive momentum, and QP modifies classical behavior of particles to quantum behavior.

The negative feature of the book is that the authors do not discuss the results of experiments they describe (see pages 11, 16, 19, and 40)

This is not a great introduction to the philosophy of quantum mechanics. It provides an inadequate explanation of the Copenhagen interpretation, and spends too much time on the weird alternatives. The discussion of photons and wave/particle duality is too short for a beginner to get a useful picture of the important issues.

The all-too-brief introduction spends far too much time on irrelevant detail, when the short space should have been devoted to quantum fundamentals. For instance, a detailed account of the Aspect experiment is surely totally inappropriate here.

The eight physicists involved are probably all the BBC could drum up at short notice. There is no mainstream representative of the Copenhagen interpretation, and the interviews leave you wishing to know what the real big hitters (Bohr, Einstein, Heisenberg...) *really* thought about these issues. To find out, you need other books.